Method of making an injection molding nozzle with tip insert

ABSTRACT

A method of making a heated injection molding nozzle with an integral tip insert. First, an inner portion, an outer collar portion, and an electrical heating element are made and integrally brazed together in a vacuum furnace using a first nickel alloy brazing material. Then a tip insert is made having a desired configuration and seated in the front end of the inner portion and a second nickel alloy brazing material is applied around it. The second brazing material has a melting temperature which is substantially below that of the first brazing material. The tip insert is then integrally brazed in place by heating them to a temperature above the melting temperature of the second brazing material and below the melting temperature of the first brazing material. In addition to not affecting the metallurgical bonding between the other components, this allows the tip insert to be easily removed for replacement by again heating the nozzle to this same temperature.

This is a Divisional of application Ser. No. 09/411,400 Filed Oct. 4,1999 which is a Continuation of application Ser. No. 09/195,095 filedNov. 18, 1998 now U.S. Pat. No. 6,009,616.

BACKGROUND OF THE INVENTION

This invention relates generally to injection molding and moreparticularly to a method of making a heated injection molding nozzlewith a tip insert.

As seen in the applicant's U.S. Pat. Nos. 4,557,685 which issued Dec.10, 1985 and 4,768,283 which issued Sep. 6, 1988, injection moldingnozzles having a tip aligned with the gate to provide hot tip moldingare well known. Apparatus having a hot tip provided by a torpedo seatedin the front end of a nozzle is also known. For instance, theapplicant's Canadian Patent Application Number 2,082,700 which was laidopen May 13, 1994 shows a torpedo having a tip held in place by a nozzleseal which slides into a seat in the front end of the nozzle. U.S. Pat.No. 5,658,604 to Gellert et al. which issued Aug. 19, 1997 similarlyshows a torpedo with a tip which is held in place by a nozzle seal whichis screwed into a seat in the front end of the nozzle. As seen in theapplicant's U.S. Pat. No. 5,494,433 which issued Feb. 27, 1996, it isalso known to have the tip provided by a side gate seal which screwsinto the nozzle.

As seen in U.S. Pat. No. 5,704,113 to Mold-Masters which issued Jan. 6,1998, a method of making a nozzle wherein an inner portion, an outercollar portion and an electrical heating element are integrally brazedtogether is also known. The applicant's U.S. Pat. No. 5,437,093 whichissued Aug. 1, 1995, shows a method wherein an injection molding nozzleis made by first brazing an inner core, an outer collar portion and anouter sleeve together by heating to a temperature above a first meltingtemperature and then casting an electrical heating element into thespace between them by heating to a temperature above a second lowermelting temperature.

The previous apparatus and methods have the disadvantage that theportion providing the tip is either screwed or pressure fitted intoplace and therefore does not provide optimal heat transfer.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to at leastpartially overcome the disadvantages of the prior art by providing amethod of making an integral injection molding heating nozzle byintegrally brazing a tip insert into a seat in the front end of theinner portion of the nozzle.

To this end, in one of its aspects, the invention provides a method ofmaking an integral heated injection molding nozzle comprising thefollowing steps. Making an elongated inner portion having a rear end, afront end, a melt bore extending therethrough from the rear end to thefront end, and a general cylindrical outer surface with a spiral grooveextending therearound. Making an outer collar portion to fit around theinner portion adjacent the rear end of the inner portion, the outercollar portion having a radial opening therethrough. Winding anelectrical heating element into the spiral groove extending around theouter surface of the inner portion and mounting the outer collar portionin place around the inner portion with a terminal portion of the heatingelement extending outwardly through the radial opening through the outercollar portion. Closing in the radial opening around the at least oneterminal portion. Applying a first brazing material having apredetermined melting temperature between the inner portion and thesurrounding outer collar portion. Integrally brazing the inner portion,the outer collar portion, and the electrical heating element together byheating them in a substantially oxygen free atmosphere in a vacuumfurnace to a temperature above the melting temperature of the firstbrazing material. Machining the integral nozzle to provide a desiredouter shape and finish. Making a seat extending around the melt bore atthe front end of the inner portion of the nozzle. Making a tip inserthaving a rear end, a rear portion extending forwardly from the rear end,a tip portion extending forwardly from the rear portion, and a melt boreextending forwardly therethrough from the rear end. The rear portion ismade to fit in the seat at the front end of the inner portion of thenozzle with the melt bore through the tip insert extending from the meltbore through the inner portion of the nozzle. Inserting the tip insertinto the matching seat at the front end of the inner portion of thenozzle. Then applying a second brazing material where the tip insert andthe inner portion of the nozzle join, the second brazing material havinga predetermined melting temperature substantially lower than the meltingtemperature of the first brazing material. Finally, integrally brazingthe tip insert in place in the inner portion by heating them to atemperature above the melting temperature of the second brazing materialand below the melting temperature of the first brazing material.

Further objects and advantages of the invention will appear from thefollowing description taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an integral heated injection moldingnozzle made according to a first embodiment the invention,

FIG. 2 is a bottom view of the heated injection molding nozzle seen inFIG. 1,

FIG. 3 is an exploded isometric view of the components that are brazedtogether in the first brazing step according to the first embodiment ofthe invention,

FIG. 4 is a sectional view showing the same components assembledtogether,

FIG. 5 is a schematic view showing the assembly from FIG. 4 in positionto be inserted into a vacuum furnace,

FIG. 6 is an isometric view showing a tip insert in position to beinserted into a seat in the front end of the nozzle according to thefirst embodiment of the invention,

FIG. 7 is an isometric view showing the tip insert seated in the frontend of the nozzle,

FIG. 8 is a sectional view showing a nozzle made according to anotherembodiment of the invention having a tip with a single angled tipportion,

FIG. 9 is a sectional view showing a nozzle made according to anotherembodiment of the invention having a tip with a pair of angled tipportions, and

FIG. 10 is an isometric view showing a nozzle made according to afurther embodiment of the invention having a tip with four angled tipportions.

DETAILED DESCRIPTION OF THE INVENTION

Reference is first made to FIGS. 1 and 2 which show an integral heatedinjection molding nozzle 10 made by a first embodiment of the presentinvention. The nozzle 10 has an elongated inner portion 12 with a rearend 14 and a front end 16. The nozzle 10 is seated in a mold (not shown)and has a central melt bore 18 extending through the inner portion 12 toconvey melt to a gate (not shown). The nozzle 10 also has an integralouter collar portion 20 which fits around the elongated inner portion 12adjacent its rear end 14. While the outer collar portion 20 is normallymade of H13 hot work tool steel, the inner portion 12 may be made of adifferent material such as stainless steel or a beryllium nickel alloyhaving different thermal characteristics to provide the nozzle 10 withthe thermal balance required for different materials being molded. Inthis embodiment, the outer collar portion 20 is made with threaded boltholes 21 to receive bolts (not shown) to secure it to a meltdistribution manifold.

The inner portion 12 of the nozzle 10 has a generally cylindrical outersurface 22 with an outwardly extending head 24 at its rear end 14. Thehead 24 fits tightly in a seat 26 in the outer collar portion 20. Theouter collar portion 20 has a circular inner flange 28 against which thehead 24 of the inner portion 12 abuts. The outer collar portion 20 alsohas a cylindrical skirt 30 which extends forwardly around but spacedfrom the outer surface 22 of the inner portion 12 to locate the nozzle10 in the mold (not shown). An integral electrical heating element 32extends in a spiral groove 34 extending around the outer surface 22 ofthe inner portion 12 of the nozzle 10. The heating element 32 hasterminal portions 36 which in this embodiment extends outwardly throughholes 38 through a terminal locating and sealing key 40 received in aslot 42 in the outer collar portion 20 of the nozzle 10.

The nozzle 10 also has a tip insert 44 brazed into a seat 46 at thefront end 16 of the inner portion 12 of the nozzle 10. The tip inserts44 are made according to this embodiment of the invention of a suitablematerial such as a tungsten carbide alloy have a rear portion 48 and onetip portion 50 with a conical outer surface 52 extending centrallyforward to a tip 54. Each tip insert 44 also has a tapered melt bore 56extending forwardly from its rear end 58 through the rear portion 48 andthe tip portion 50. As can be seen, in this embodiment the melt bore 56through the tip insert 44 has a rear portion 58 aligned with the centralmelt bore 18 through the inner portion 12 of the nozzle 10 and a frontportion 60 extending diagonally outward to the outer conical surface 52.The rear portion 48 of the tip insert 44 and the matching seat 46 at thefront end 16 of the inner portion 12 made according to this embodimentof the invention are cylindrical. However, in other embodiments of theinvention they can have other suitable matching shapes.

The integral heated nozzle 10 also has a locating and sealing ringstopper sleeve 62 integrally mounted around the cylindrical outersurface 22 of the inner portion 12. This allows a ribbed locating andsealing ring 64 to be removably mounted to abut against a forwardlyfacing outer shoulder 66 extending around the locating and sealing ringstopper sleeve 62.

Reference will now also be made to FIGS. 3-6 to describe a method ofmaking the integral heated injection molding nozzle 10 according to oneembodiment of the invention. Firstly, the components of the integralheated nozzle 10 are made as shown in FIG. 3. The inner portion 12 ofthe nozzle 10 is made of a suitable material such as H13 tool steel tohave the generally cylindrical outer surface 22 with the spiral groove34 in it and the outwardly extending head 24 at its rear end 14. Theinner portion 12 is made by conventional machining or by metal injectionmolding. The outer collar portion 20 is made with the inner flange 28which fits around the inner portion 12 and has the slot 42 providing aradial opening therethrough. The outer collar portion 20 is similarlymade by conventional machining or by metal injection molding of asuitable material such as H13 tool steel, stainless steel or a berylliumnickel alloy.

In this embodiment, the locating and sealing ring stopper sleeve 62 ismade similarly of a suitable material such as H13 tool steel. It is madewith the forwardly facing outer shoulder 66 and a cylindrical innersurface 68 which fits over the cylindrical outer surface 22 of the innerportion 12. The terminal locating and sealing key 40 having the holes 38through it and a pin portion 70 extending inwardly therefrom is madesimilarly of a suitable material such as H13 tool steel to fit in theslot 42 in the outer collar portion 20. The heating element 32 is madein a conventional manner with insulative compacted magnesium oxidepowder extending around a central resistance wire in an outer stainlesssteel casing 72.

As best seen in FIG. 6, the tip insert 44 is made by machining it of asuitable material such as a tungsten carbide alloy. In this embodiment,it is made to have a rear portion 48 and a single tip portion 50 with aconical outer surface 52 extending centrally forward to a tip 54. It ismade with a tapered melt bore 56 having a central rear portion 58 and afront portion 60 extending diagonally outward from the rear portion 58to the outer conical surface 52.

Next, the electrical heating element 32 is wound in the spiral groove 34in the outer surface 22 of the inner portion 12. The inner portion 12 isthen inserted through the outer collar portion 20 with the head 24 ofthe inner portion 12 abutting against the circular inner flange 28 ofthe outer collar portion 20 and the terminal portions 36 of the heatingelement 32 extending out through the slot 42 in the outer collar portion20. The locating and sealing ring stopper sleeve 62 is mounted aroundthe inner portion 12 and tack welded in place adjacent the front end 16of the inner portion 12. The two terminal portions 36 of the heatingelement 32 are inserted through the two holes 38 and the terminallocating and sealing key 40 is pushed inwardly to its assembled positionin the matching slot 42 in the outer collar portion 20 with the pinportion 66 received in a hole 74 in the inner portion 12. Then, with theassembled components in the upright position shown in FIG. 4, a quantityof a first conductive brazing material having a suitable meltingtemperature such as a nickel alloy powder 76 is poured into the space 78between the cylindrical outer surface 22 of the inner portion 12 and theskirt 30 of the outer collar portion 20. A bead 79 of the firstconductive brazing material such as a nickel alloy paste 79 is appliedat the front end 16 of the inner portion 12 adjacent the locating andsealing ring stopper sleeve 62.

The assembled components are then loaded (usually in batches) into avacuum furnace 80 as seen in FIG. 5. As the vacuum furnace 80 isgradually heated to a first temperature of approximately 1950° F. whichis above the melting point of the first nickel alloy brazing materialpowder 76 and paste 79, it is evacuated to a relatively high vacuum toremove substantially all of the oxygen. The vacuum is then reduced bypartially backfilling the vacuum furnace 80 with an inert gas such asargon or nitrogen to avoid sputtering. This melts the first nickel alloybrazing powder 76 which flows by capillary action upwardly along theheating element 32 in the spiral grooves 34 and also between the innerportion 12 and the outer collar portion 20. It also melts the firstnickel alloy brazing paste 79 which flows by capillary action betweenthe inner portion 12 and the locating and sealing ring stopper sleeve 62to integrally braze them all together. Brazing them together like thisin a partial vacuum produces a metallurgical bonding of the nickel alloybrazing material 76 between them which in turn provides improved heattransfer between them.

After cooling, the integral nozzles 10 are removed from the vacuumfurnace 80 and a tip insert 44 is mounted in place with its rear portion48 in the matching seat 46 at the front end 16 of the inner portion 12of the nozzle 10. A second conductive brazing material 82 such as asilver alloy having a suitable melting temperature substantially belowthe melting temperature of the first brazing material 76 is then appliedaround the tip insert 44 and the nozzles 10 are again loaded in batchesinto the vacuum furnace 80. In other embodiments, copper or brass typealloys having a melting temperature substantially below the meltingtemperature of the first nickel alloy brazing material 70 can be used.The vacuum furnace 80 is then gradually heated to a second temperatureof approximately 850° F. which is above the melting temperature of thesecond silver alloy brazing material 82 but below the melting point ofthe first conductive brazing material 76. As the vacuum furnace 80 isgradually heated it is again evacuated to a relatively high vacuum toremove substantially all of the oxygen. The vacuum is then reduced bypartially backfilling the vacuum furnace 80 with an inert gas such asargon or nitrogen to avoid sputtering. This melts the second silveralloy brazing material 82 which runs between the tip insert 44 and thesurrounding inner portion 12 of the nozzle 10 to integrally braze themtogether. Brazing them together like this in a partial vacuum produces ametallurgical bonding of the silver alloy brazing material 82 betweenthem to provide an integral injection molding heated nozzle 10 havingvery improved thermal characteristics. However, in an alternateembodiment of the invention, the tip insert 44 can be integrally brazedin place (or removed) by heating the nozzle 10 to the second temperatureof approximately 850° F. just using the integral heating element 32without insertion into the vacuum furnace. While a silver alloy secondbrazing material 82 is used in this embodiment, in other embodiments acopper alloy or other suitable second brazing material 82 can be used.The silver alloy second brazing material 82 having a melting temperaturesubstantially below the melting temperature of the nickel alloy firstbrazing material 76 allows the tip insert 44 to be integrally brazed inplace without melting the nickel alloy first brazing material 76.Similarly, it allows the tip insert 44 to be removed for replacement byagain heating the nozzle 10 to this same second temperature withoutaffecting the metallurgical bond between the other components of thenozzle 10.

The integral heated injection molding nozzle 10 is then machined to giveit the desired outer shape and finish.

In use, the integral heated injection molding nozzle 10 is attached to amelt distribution manifold mounted in a mold (not shown) and electricalpower is applied to the heating element 32 to heat it to a predeterminedoperating temperature. Pressurized melt is applied to the meltdistribution manifold from a molding machine (not shown) according to apredetermined injection cycle. The melt flows through the central meltbore 18 in the heated nozzle 10 and the aligned melt bore 56 in the tipinsert 44 to a gate (not shown) leading to a cavity in the mold. Afterthe cavities are filled and a suitable packing and cooling period hasexpired, the injection pressure is released and the melt conveyingsystem is decompressed to avoid stringing through the open gates. Themold is then opened to eject the molded products. After ejection, themold is closed and the cycle is repeated continuously with a cycle timedependent upon the size of the cavities and type of material beingmolded.

Reference is now made to FIG. 8 which shows another embodiment of themethod of making a integral heated injection molding nozzle 10 having anintegral tip insert 44. In this embodiment, the tip insert 44 is madewith the tip portion 50 extending diagonally outward from the rearportion 58 and the melt bore 56 extending centrally therethrough. Theremainder of the method is the same and need not be repeated.

Reference is now made to FIG. 9 which shows another embodiment of themethod of making an integral heated injection molding nozzle 10 havingan integral tip insert 44. In this embodiment, the tip insert 44 is madewith a pair of tip portions 50 extending diagonally outward from therear portion 48 and the melt bore 56 extending centrally therethrough.As can be seen, the tip portions 50 are made with a shape and size thatallows the ribbed locating and sealing ring 64 to fit over them.

Reference is now made to FIG. 10 which shows a further embodiment of themethod of making an integral heated injection molding nozzle 10 havingan integral tip insert 44. In this embodiment, the tip insert 44 is madewith four tip portions 50 extending diagonally outward from the rearportion 48 and the melt bore 56 extending centrally therethrough. Thenozzles 10 shown in FIGS. 8, 9 and 10, wherein the tip insert 44 has oneor more tip portions 50 extending diagonally outward, all have a pin 84extending between the tip insert 44 and the inner portion 12 of thenozzle 10 to locate the tip insert 44 relative to a reference bore 86 inthe outer collar portion 20 shown in FIG. 1. This enables the nozzle 10to be mounted with each tip 50 very accurately aligned in the center ofthe gate.

While the description of the method of making the integral heatedinjection molding nozzle 10 has been given with respect to preferredembodiments, it will be evident that various other modifications arepossible without departing from the scope of the invention as understoodby those skilled in the art and as defined in the following claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed is defined as follows:
 1. A method of making aninjection molding nozzle comprising the steps of: making an innerportion having a melt bore extending therethrough, a front end, an outersurface, and a heater groove in the outer surface; placing a heaterelement in the heater groove; metallurgically bonding the heater elementto the inner portion using a first bonding material; and thenmetallurgically bonding a tip insert to the front end of the innerportion using a second bonding material, wherein the second bondingmaterial has a lower melting temperature than the first bondingmaterial, and the step of metallurgically bonding the tip insertcomprises heating the inner portion and the tip insert to a temperaturethat is above the melting temperature of the second bonding material andbelow the melting temperature of the first bonding material so as not todisrupt the metallurgical bond between the heater element and the innerportion.
 2. A method of making an injection molding nozzle according toclaim 1, wherein the metallurgical bonding steps comprise brazing theheater element and the tip insert to the inner portion.
 3. A method ofmaking an injection molding nozzle according to claim 2 wherein the tipinsert has at least one tapered front tip.
 4. A method of making aninjection molding nozzle according to claim 3, wherein the at least onetapered front tip extends diagonally outwardly.
 5. A method of making aninjection molding nozzle comprising the steps of: making an innerportion with a melt bore extending therethrough, the inner portionhaving a front end and a rear end; placing a collar portion around theoutside of the inner portion; metallurgically bonding the collar portionto the inner portion using a first bonding material; and thenmetallurgically bonding a tip insert to the front end of the innerportion using a second bonding material, wherein the second bondingmaterial has a lower melting temperature than the first bondingmaterial, and the step of metallurgically bonding the tip insertcomprises heating the inner portion and the tip insert to a temperaturethat is above the melting temperature of the second bonding material andbelow the melting temperature of the first bonding material so as not todisrupt the metallurgical bond between the collar portion and the innerportion.
 6. A method of making an injection molding nozzle according toclaim 5, wherein the metallurgical bonding steps comprise brazing thecollar portion and the tip insert to the inner portion.
 7. A method ofmaking an injection molding nozzle according to claim 6, wherein the tipinsert has at least one tapered front tip.
 8. A method of making aninjection molding nozzle according to claim 7, wherein the at least onetapered front tip extends diagonally outwardly.
 9. A method of making aninjection molding nozzle according to claim 8, wherein the collarportion is brazed adjacent the rear end of the inner portion.
 10. Amethod of making an injection molding nozzle according to claim 7,wherein the collar portion is brazed adjacent the rear end of the innerportion.